Many devices include a control panel having a plurality of controls that set the manner in which the device operates. Traditionally, the controls were implemented using switches and potentiometers to provide inputs to the controller that supervises the device functions. These physical input devices were typically mounted on a panel and connected by wires to the controller. Such control panels were customized devices that were only used on one or, at most, a few devices. In essence, each device required a custom control panel. The need for such custom panels increased the cost of the device and the time needed to develop and market a new device.
With the advent of touch screen displays, the problem of providing a control panel has been greatly reduced, since a single touch screen can be programmed to provide a custom control panel for the associated device. In addition, the control functions of many devices are implemented by computers, and hence, the control panel and computer can be provided by programming the computer to provide a display that emulates the “controls” of the traditional control panel and detects the user's interaction with the touch screen to provide the desired changes in the device functions.
For example, a dial that sets the volume of a sound system can be implemented by displaying a picture of a dial on the touch screen. The user touches the dial with a finger and moves the finger to simulate moving the dial. The computer then alters the corresponding control parameter by an amount determined by the degree of movement input by the user. In addition, the computer changes the position of the dial in the display to reflect the new value of the control parameter. Since the display and input regions of the screen are determined by the software, the same touch screen and control computer can be used to control a large range of instruments or other devices.
While such emulated control panels are a significant improvement over conventional panels constructed from dials and the like, there are still significant limitations, particularly when implementing controls that require fine adjustments or panels that require a large number of distinct controls. The resolution of a touch screen is limited by the size of the user's finger and the physical resolution of the screen touch sensor.
To provide fine resolution, the dial must move a distance that is large compared to the smallest distance that the computer can detect with respect to movement of the finger on the screen. Furthermore, the contact area on the screen depends on the pressure with which the user presses the user's finger on the screen. Hence, to simulate a dial that can be positioned with a high degree of accuracy, the size of the emulated dial must be large compared to the size of the user's finger. Accordingly, large screens are preferred for such sensitive applications. Unfortunately, there are limitations to the size of the screens that can be used. The cost of the screens increases rapidly with size. In addition, the device being controlled can constrain the size of the screen. Hence, for many applications, there is a limit to the number of high resolution controls that can be implemented at any one time on the touch screen.
To provide a large number of functions, the touch screen is typically used in a “mouse” mode in which items are selected from lists that are implemented as pull-down menus. For systems having many functions, the menus are typically organized as a hierarchy of nested menus. Such schemes require the user to learn the sequence of menus to arrive at any desired control parameter that is to be adjusted.